Beam modal corner identification and damage diagnosis method based on fiber bragg grating test

The invention discloses a beam modal corner identification and damage diagnosis method based on a fiber grating test, and the method comprises the steps: obtaining the long gauge length time domain strain of a beam structure under a dynamic load through the distributed arrangement of long gauge length fiber grating strain sensors at the bottom of the beam structure in the length direction; the method comprises the following steps: theoretically deriving a relationship between long-gauge-length time domain strain and a time domain rotation angle, then converting the time domain rotation angle of a structure into a frequency domain rotation angle (namely a modal rotation angle) through Fourier transform, and establishing a damage diagnosis method based on a normalized modal rotation angle difference. The method can be used for long-distance, large-range and high-precision online monitoring, is high in modal rotation angle measurement precision and damage diagnosis sensitivity, is suitable for any dynamic load,